I survived entirely on the mobile ap for about three years and over 3,000 subs. So it can be done! I would suggest of course that the paid, Unlimited mobile features are a little more robust but all of these features are included in the Mobile App:
Video stats,
comments
Milestones
Industry news
Tag explorer
Topic planner
Canned responses
Tag lists
Video best practices
Video tag rankings/editing
Video promo materials
Videolyrics